1. Field of the Invention
The present invention relates to monitoring parameters associated with manufacturing processes. More particularly, the present invention relates to automatically measuring and storing parameters related to the printed circuit board (PCB) manufacturing process.
2. Description of Related Technology
Printed circuit boards are currently manufactured at a number of sites in a number of countries. Although PCB manufacturing might be arguably a xe2x80x9cmaturexe2x80x9d industry, the conventional manufacturing procedures do not solve the current demands for lower cost and higher quality printed circuit boards.
By way of specific example, during one step of PCB manufacturing common to a plethora of manufacturing sites, a resist layer is laid on top of the surface of a copper panel. In order to provide adequate protection to the underlying copper substrate during a subsequent etching phase, the resist must conform to the surface topography of the copper such that there are no voids or areas in which the resist does not protect the copper. FIG. 1A illustrates ideal conformation between the surface of a copper panel 10 and a resist 12. Note that there are no voids, or air pockets, between the resist 12 and the surface of the copper panel 10. While the conformation shown in FIG. 1A is the goal of all manufacturing sites, FIG. 1B, however, shows a more typical conformation which is achieved between a resist 12 and the copper panel 10. As can be seen in FIG. 1B, air is entrapped between the resist 12 and the surface of the copper panel 10, thereby forming interfacial voids 14. During the following etching process, the etchant solution seeps under the resist 12 where interfacial voids 14 are located and attacks the copper which should have been protected by the resist 12. After etching is complete, a conductive trace is either narrowed or broken because of the attack which occurred at the interfacial void 14 during etching.
The preferred embodiment of the present invention provides a system and method for automatically monitoring the manufacture of printed circuit boards and automatically monitoring the critical PCB process parameters within quality control limits. However, it is understood that the method and system of the invention may be utilized in other areas of technology which requires the collection, monitoring and/or analysis of statistical data. The science of statistics relates to the gathering of data, or numerical values, for purposes of analysis in order to ascertain numerical facts. The present invention provides a statistical process control integration system (SPCIS) in which monitored machinery associated with various manufacturing and/or testing processes are coupled to a central controller which receives measured process parameters and stores this data. The controller may also run the protocol for data measurement and transmission from each piece of machinery to the controller. The measured process parameters may serve as certifiable data within the process which can be systematically downloaded into a text or other suitable format approved by the International Standardization Organization (ISO), for example, for quality assurance certification. The SPCIS of the invention can also allow the measured parameters to be stored in a memory such that historical information related to the manufacturing process may be saved. Additionally, the SPCIS can notify manufacturing and/or engineering personnel of pending problems, or lack thereof, on a real-time basis.
The invention also provides a method and system, or network, for interconnecting multiple, remotely located, PCB manufacturing sites such that these remotely located processes may be monitored in a coordinated fashion. By utilizing computer-based networks such as a local area network (LAN) and/or a wide area network (WAN), or the global computer information network, otherwise known as the xe2x80x9cInternet,xe2x80x9d a system operator at a remote location can access an SPCIS server computer and perform monitoring functions and access data as if that system operator were physically in the room where the SPCIS monitoring equipment are located. Therefore, the invention also provides an automatic and computerized system which can electronically link multiple remote sites in order to efficiently monitor process parameters at each of the remote sites and correlate the measured data such that an accurate record of each PCB, or batch of PCBs, and the corresponding process parameters measured during the manufacture of the PCBs can be maintained.
The systems and methods of this invention provide significant advantages. Typically, under prior art monitoring techniques, a human operator manually measures a specific set of parameters and records these measured values into a log book. This process is tedious and time-consuming. As human resources are limited, the monitoring and maintenance of the various process parameters described above can not be frequently performed using this prior art, manual method. Depending on the human resources of a particular company, only a select few of these process parameters are typically measured. Additionally, they are measured and recorded on an infrequent basis (e.g., daily, weekly or even monthly).
Often times, if a process parameter is not within specified limits, it is detected only after many PCBs have been manufactured defectively. These defective PCBs typically need to be reworked or, if the damage is too extensive, discarded entirely. This leads to a waste in materials, time and resources of the company. Additionally, since manufacturing process parameters are not frequently monitored, real-time alarms and displays which warn a system operator of out-of-tolerance parameters are not provided by the prior art systems. If a process parameter is out of tolerance, there is no alarm or way of notifying a quality control engineer until the out of tolerance process parameter is detected by an operator whose job is to manually perform routine measurements of the process parameters at intermittent time periods. By the time the out of tolerance process parameter is detected, many defective PCBs may have already been manufactured.
A feature of this invention is that it provides an efficient and automated method and system for monitoring process parameters related to the PCB manufacturing process such that desired process parameters may be frequently monitored in order to provide real-time alarms which may notify an operator as soon as an out of tolerance parameter is detected. Additionally, this invention provides an automatic method and system for recording and storing measured process parameters such that an accurate history of the conditions under which a particular batch of PCB""s are manufactured may be maintained. By providing a record of values of measured process parameters which correspond to each batch of PCBs, a manufacturer can provide quality control data to customers for each batch of PCBs.
With the emergence of a world-wide global economy, many PCB manufacturers have an international client base. For these manufacturers, PCBs that are manufactured and sold in the United States, and in other countries, must meet quality control specifications promulgated by organizations such as the International Standardization Organization (ISO). The ISO requires that with each shipment of PCBs, a certified record of the quality control tests and their results related to each batch of PCBs be included. With such requirements by organizations such as the ISO, it is now more important than ever to provide an efficient, comprehensive and reliable method and system for monitoring the process parameters of the PCB manufacturing process. The present invention eliminates the need for tedious manual measurement and recording of parameters associated with the statistical process control procedures of the prior art.
Additionally, prior art PCB manufacturing methods do not provide any way of efficiently consolidating and organizing the measured process parameters into a comprehensive and meaningful format for enabling a customer, or other end user, to quickly view and evaluate the conditions under which a given batch of PCBs were manufactured. This invention provides a method and system for automatically consolidating, correlating and organizing measured process parameters in order to present the data in a format which is meaningful and easy to understand. For example, measured temperature values may be represented by a historical bar graph which may be quickly and easily viewed by a system operator.
Another significant feature of one embodiment of the invention is an automated and computerized system which may link multiple remote sites in order to efficiently monitor the process parameters at each of the remote sites and correlate the measured data such that an accurate record of the batch number of the PCBs, the location of the manufacturing site, the values of the process parameters taken from each site, etc. can be maintained. Prior art methods do not accommodate a systematic and coordinated method of monitoring and measuring process parameters at these different locations. Often times, when a company has several manufacturing plants or sites, it is difficult to monitor the above-identified process parameters and maintain quality control over the manufacturing processes at each of the sites. Prior art methods require a separate operator to measure and record these parameters at each of the sites. However, this invention makes it now possible to link many remote manufacturing sites such that data may be communicated between multiple remote sites and a central computer, or server, which can process and store the data. Prior art statistical process control systems do not integrate multiple remote process sites so as to monitor the remote sites in a coordinated fashion.